Family accommodation is associated with an increase in anxiety and has recently received attention as a target for intervention for youth anxiety. Existing theories posit that the increase in family accommodation increases youth anxiety and can attenuate the effect of psychotherapy. However, the directionality between family accommodation and youth anxiety has not been investigated. A cross-lagged cross-panel design was used to assess accommodation and anxiety for 10 sessions for 73 youths with an anxiety disorder, who were receiving cognitive-behavioral therapy. The analysis revealed a bidirectional relationship, such that to some extent previous session family accommodation increased youth anxiety symptoms (β = 0.11, 95% CI [0.06, 0.17]), but to an even greater extent previous session youth-rated anxiety symptoms increased family accommodation (β = 0.23, 95% CI [0.08, 0.38]). Family accommodation is an important target for reducing youth anxiety but should be addressed simultaneously as interventions directly targeting youth anxiety.